Perspective from Dmitriy Kedrin, MD, PhD
September 13, 2019
1 min read

FDA approves Ibsrela for IBS-C in adults

Perspective from Dmitriy Kedrin, MD, PhD
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The FDA on Thursday approved Ibsrela, a 50 mg, twice-daily oral therapy for irritable bowel syndrome with constipation in adults.

“Ibsrela has the potential to provide IBS-C patients and their doctors with a novel mechanism and an innovative approach to managing IBS-C, a highly burdensome and difficult-to-treat condition affecting more than 11 million people in the United States,” Mike Raab, president and CEO of Ardelyx, said in a company-issued press release.

The approval of tenapanor (Ibsrela, Ardelyx) — a minimally absorbed small molecule that acts locally in the gastrointestinal tract to inhibit the sodium-hydrogen exchanger NHE3 — is based on data from two phase 3, randomized, double-blind, placebo-controlled trials.

Both trials were identical through the initial 12 weeks of therapy. One of the trials continued for an additional 14 weeks of treatment, whereas the other trial included a 4-week randomized withdrawal period.

Proportion of patients who responded to the therapy during the 12-week treatment period served as the primary endpoint. A patient was considered a responder if they experienced at least a 30% reduction in weekly average abdominal pain score compared with baseline and an increase of at least one complete spontaneous bowel movement in weekly average from baseline, in the same week, for at least 6 of the first 12 treatment weeks.

In the first trial, 37% of patients receiving tenapanor met the primary endpoint compared with 24% of patients receiving placebo. Twenty-seven percent of patients receiving tenapanor in the second trial met the primary endpoint compared with 19% of patients receiving placebo.

The most common adverse event in both studies was diarrhea — 16% with tenapanor vs. 4% with placebo in trial 1, 15% with tenapanor vs. 2% with placebo in trial 2.

Tenapanor is contraindicated in patients younger than 6 years. The safety and efficacy of tenapanor in patients younger than 18 years has not yet been established.

The contraindication is based on a study of young juvenile rats, which demonstrated that tenapanor caused death presumed to be due to dehydration, according to the release.